White Papers

Back to Basics: Feed Forward Curve Fitting

Feed Forward Curve Fitting Using a Process Dataset 1. Curve Fitting to a Dataset: As a complement to my last whitepaper, Modeling And Scaling Feedforwards, I have written this paper to discuss one of the approaches toward creating feedforward models. Many times it is not possible or practical to develop a mathematical relationship between the Read more…

Back to Basics: Modeling and Scaling Feedforwards

Modeling and Scaling Feedforwards Depending on the complexity and precision requirements of the process, the resulting control arrangement can range from simple “Process Value > Controller > Manipulated Variable control” to a feedforward or cascade control. In this paper I will discuss the considerations when to utilize feedforwards, cascades and the scaling associated with these control additions. Read more…

Density Compensation of DP Flow Meters

Density Compensation of Differential Pressure Flow Meters By Wayne Salo The most elegant programming or control configuration is wasted if the fundamental physics, chemistry or mechanics is not understood. If you cannot measure it properly, you cannot control it properly. (Garbage In, Garbage Out – GIGO) The control engineer or technician must understand the fundamentals Read more…

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Power Plant Control Systems

Power Plant Control Systems By Wayne Salo Over the past 40+ years I have been involved with the design, specification, installation, maintenance and tuning of boiler/turbine combustion control systems and plant auxiliary systems. Over the years I have observed that companies have not been hiring or replacing control engineers in a timely fashion to provide Read more…

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Wayne Salo

Wayne Salo joined Excel Engineering in 2012 with over 41 years in the power industry. These include over 6 years with Combustion Engineering Inc. in Windsor, CT as a field service engineer providing checkout and start-up of boilers, fuel firing equipment, scrubbers and associated fuel interlocks and controls. Wayne was hired by Northern States Power Read more…

White Paper Disclaimer

Disclaimer: The content provided in these white papers is intended solely for general information purposes, and is provided with the understanding that the authors and publishers are not herein engaged in rendering engineering or other professional advice or services.  The practice of Engineering is driven by site-specific circumstances unique to each project.  Consequently, any use Read more…

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Basic humidity made easy

Definitions There are several common terms that we use in our normal conversation but do not necessarily know what they actually mean. These are Dry Bulb Temperature, Wet Bulb Temperature, Relative Humidity, Dew Point Temperature and Adiabatic Saturation Temperature. Several discussions in the recent past have caused me to explain to others what many of Read more…

Grinding, Drying & Transport 4

Creating a control arrangement with constraints As we noted previously it is important to have a good measurement of the air flow through the system. We need to be able to accommodate the design criteria and respect the system limits. We will need to compensate for the inlet temperature but will not actively compensate for Read more…

Grinding, Drying & Transport 3

Accommodating Process Dynamics Depending on the material being ground or pulverized, maintaining the through-flow of the ground product to its destination is important. Depending on the particular process, it may be of benefit to either maintain a constant flow of the product through the transport lines or you may need to dynamically change the amount Read more…

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Grinding, Drying & Transport 2

Analysis of the flow measurement As we noted in the Phase 1 of this series we need to maintain at least minimum air flows throughout the piping and grinding process to prevent dropout of particles in the transport piping or within the grinder/pulverizer. We must check the sensitivity of the measurement. Typically the flow measurement Read more…

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Grinding, Drying & Transport 1

Designing Controls In this project we will be designing controls associated with equipment designed to take a coarse product, grind, pulverize and classify the material to the proper consistency (like that of face powder), dry it and then transport the material to a receiving process. If the material being processed is combustible, the control of Read more…

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Hot Water Project: Phase 4

As we noted in the last hot water project blog, the customer noted that the steam pressure varied and the steam control valve position did not necessarily represent the steam flow to the heater. Let’s get the steam under control. We tell the customer that the addition of instrumentation to the steam lines will cost Read more…

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Hot Water Project: Phase 3

As we noted in the last blog, the customer noted that the water pressure varied and the water control valve position did not necessarily represent the flow through the heater. The customer has indicated that they would be able to release some additional funds for process instrumentation. At this time a flow measurement of the Read more…

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Hot Water Project: Phase 2

As we noted in the last blog, the customer has told you he is unhappy with the temperature control of the process water. After signing a telephone book of nondisclosure agreements the customer has offered additional information regarding his process. During the past months of operation they have been able to characterize the efficiency of Read more…

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Hot Water Project, Phase 1

One of the more common projects is to heat water (or some other liquid) from a random cold temperature to a desired working temperature. The inevitable discussion occurs with your boss or the customer regarding the usual items – schedule, scope and costs. If you are lucky, the customer has properly identified the scope of Read more…

Participation of Multiple Elements

There are times in larger processes when many like-type devices must be used in parallel to achieve the desired through-put to adequately supply the process. Either the applicable equipment technology has not evolved to provide the through-put or the equipment has reached its technological limits and cannot be manufactured or increased in size without decreasing Read more…

Extend Valve Control Flow Range

Extend the valve control flow range with staged valves A single valve may not have the resolution needed to adequately control the process. Another example is while dealing with large flows requiring precise control over the whole flow range. Providing a single valve with the required Cv (effective valve flow coefficient) characteristics may be extremely Read more…

Why We Need to Know the Basics

As you may have noticed, my blog posts are often triggered by questions and real life situations.  That is the case with today’s post. Some manufacturer’s web sites are VERY difficult to navigate.  Due to this fact, I will sometimes ask for sales or technical assistance instead of wasting too much time searching a vendor web site Read more…

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Safety Barriers and Thermocouples

Why do I need safety barriers when I’m using thermocouples? It meets the definition of a simple apparatus.  I think the barrier sales people are simply looking for more sales! When I was asked this question, I thought I could use this example to provide some insight into the requirements of intrinsic safety systems. An Read more…

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Control the Flow

Control the flow – select an appropriate valve trim Normally when the process or mechanical engineer designs the process and selects the individual components, they may not necessarily select the proper trim characteristics that would properly complement the control design. A valve and trim selection training course could cover several days and will not be Read more…

Spare Transformers

Spare Transformers: Why, how many, and how to compute it all? Purpose of Spare Transformers Spare transformers are kept in stock so that failed units can be replaced relatively quickly.  Absent a spare, most large power transformers have a replacement or repair time of at least 9 – 12 months.  On the transmission system, failure Read more…

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Pumps and Flow Problems

Pumps will perform as designed and last a long time as long as we respect their limitations and treat them well. There are several parameters that the mechanical or process engineer and control designer need to understand and respect. These parameters include: 1. NPSHRequired and NPSHAvailable 2. Minimum Stable Flow 3. Pump Curves 4. Best Read more…

Starting a new control project

It is interesting to note that control projects generally fall into two categories: 1. A new control process or 2. Enhance or copy an existing control process. Tackling either of these options need to follow a similar approach. Sometimes the individuals tasked with these projects feel that they can worry about the details later. “I’ll Read more…

Rick Gonzalez

The late Rick Gonzalez joined Excel Engineering in 2003 with over 20 years’ experience in electric power system planning and analysis before his passing in 2012. In his previous positions at Northern States Power/Xcel Energy (Minneapolis, MN) and the Western Area Power Administration (Golden, CO), Rick performed short and long-range planning studies for local and regional Read more…

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Mark Mathews

Senior Specialist in the Controls and Instrumentation Mark Mathews joined Excel in 2011 as a Senior Specialist in the Controls & Instrumentation discipline.  He has 23 years of experience in providing control system solutions to 3M and a broad array of other clients.  In that time, he has developed project execution skills that begin with Read more…

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Intrinsic Safety Standards Update

ISA S12.2 subcommittee meeting report Spring, 2012 The work of harmonizing the Hazardous Area national standards of the United States with those of the international community continue in earnest. The ultimate goal of this harmonization is that products produced and approved in the US can be exported and installed in other countries, and vice versa. Read more…

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Series Compensation

Series Compensation: The Under-Appreciated Transmission Improvement Everyone wants better line and system performance The usefulness of a transmission line is limited by its thermal rating (ampacity), and its series impedance. The ampacity can be increased by installing larger conductor; installing multiple conductors per phase (“bundled conductors”); installing conductor capable of withstanding higher operating temperatures. From this list it Read more…

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Subject Matter Experts

For your reference, the following subject matter experts are providing content on the respective blog: Controls – Wayne Salo: Wayne Salo joined Excel Engineering in 2012 with over 41 years in the power industry. These include over 6 years with Combustion Engineering Inc. in Windsor, CT as a field service engineer providing checkout and start-up Read more…

Knowledge Base

Knowledge Base from Excel Engineering Excel Engineering continues to strive to bring the highest value to our clients through the excellent people that are part of our organization. We have several technical experts who want to share their knowledge. Please view the controls and intrinsic safety Excel Engineering blog categories for more information in these Read more…

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